I just finished the NP249 to NP231 Transfercase swap in my '94 ZJ Limited 5.2! I thought I would let you all know what I ran into and how it went, for anyone thinking of doing this.
- I found the NP231 in a 1993 Cherokee 6 cylinder - 5 speed at a salvage yard. I chose the NP231 because it is a little stronger and there are fewer parts inside so fewer parts to break. It is also much easier and cheaper to rebuild one if needed. It cost me $200 and I took it out of the jeep myself...all you need are the necessary tools, prybar, and a jack.
- I did end up having to swap the input shaft, my old 249 had the longer style and the 231 had the short. I took apart the NP249 first so if I made a mistake it wouldn't matter. I took the input shaft from the 249 and put it in the 231, the gear cuts were the same.
- The new t-case went in great! The only problem I had was with the linkage. I did not change the shifter tab on the 231. The stock linkage in my ZJ fit "almost" perfectly. First I had to cut the front part off the plastic slider that is around the t-case shifter in the cab to allow the shifter to move far enough forward. Then I had to grind away a peice of the metal gate/bracket to also allow the shifter to go far enough forward. The rod that connects the linkage to the tcase was a little too long to fully allow the case to shift into 2HI, even with the modifications made to the parts around the shifter. I simply cut it in half with a small cutting wheel and welded it back together. I only removed 1/16th to 1/4 inch of material...about the width of the cutting wheel. You do not need to be a good welder to weld it back together...or even have a good welder to do it with. Now it fits perfect!
I did not have to adjust my driveshafts or anything else. I am really glad I went this way and did not try to fix the NP249. The ZJ goes down the road a lot smoother being able to be in fulltime 2WD. The only issue I still have is with the speedometer but I am working to get that straightened out...I think I may just need a different speedo gear in the t-case.
Hope this helps anyone thinking of doing the swap! Feel free to email me with any questions. I also have a short, old style gear cut(I am assuming) input shaft if anyone needs one.